Physical Quantity Sensor

ABSTRACT

To provide a physical quantity sensor in which the influence of deformation of a package substrate on the measuring accuracy of a sensor element can be suppressed. A physical quantity sensor includes a sensor element that detects a predetermined physical quantity and outputs an electrical signal, a plurality of lead portions that are connected to the sensor element, and a package substrate that accommodates the sensor element and the plurality of lead portions. The plurality of lead portions are connected at proximal end sides thereof to the package substrate side, and connected at distal end sides thereof to the sensor element side, and the plurality of lead portions support the sensor element in such a manner that the sensor element does not contact the package substrate and that the transmission of deformation of the package substrate side to the sensor element is suppressed.

TECHNICAL FIELD

The present invention relates to a physical quantity sensor.

BACKGROUND ART

Physical quantity sensors whose measurement target is a physicalquantity such as acceleration are manufactured using amicro-electro-mechanical systems (MEMS) technique. The physical quantitysensor is, for example, a minute three-dimensional structure that isprocessed using techniques such as deposition, photolithography, andetching to which a semiconductor manufacturing process is applied. Whena signal (pressure, acceleration, angular velocity, etc.) from theoutside acts on the three-dimensional structure of the physical quantitysensor, the physical quantity sensor outputs an electrical signal inresponse to the deformation amount of the three-dimensional structure.

A physical quantity sensor disclosed in PTL 1 is composed of beams, aweight, and detection electrodes. In the physical quantity sensor of PTL1, when a signal (acceleration, angular velocity) from the outside isapplied, the weight connected to the beams is driven. The physicalquantity sensor detects a change in capacitance between the detectionelectrodes due to the driving of the weight, and outputs a signal.

As in a physical quantity sensor disclosed in PTL 2, piezoresistiveelements may be formed instead of detection electrodes in beams. In thephysical quantity sensor disclosed in PTL 2, when a weight is driven bya signal from the outside, the resistance value of the piezoresistiveelement changes, and as a result of this, a voltage changes. In thismanner, the physical quantity sensor can detect a physical quantity as achange in capacitance or a change in voltage.

By the way, when temperature, humidity, unwanted vibration or the likeother than a detection target is applied to the physical quantity sensorat the time of detecting a physical quantity as a measurement target, apackage substrate or the like is deformed. This deformation adverselyaffects the measuring accuracy for the physical quantity as an originalmeasurement target.

In PTL 3, in an angular velocity sensor in which a vibration-typeangular velocity detecting element is accommodated in a packagesubstrate, the resonant frequency of leads is lowered by lengthening alead frame. Due to this, in the angular velocity sensor disclosed in PTL3, the influence of the resonant frequency of the leads on a highresonant frequency (several thousands Hz) is reduced.

In PTL 4, an anti-vibration member is provided between an internal unitand a casing of a dynamic quantity sensor. The dynamic quantity sensordisclosed in PTL 4 absorbs vibration transmitting from the casing withthe anti-vibration member, and transmits only vibration as a measurementtarget to the internal unit.

In NPL 1, an angular velocity sensor chip is mounted in a suspendedmanner in a packaging by wire bonding. Due to this, in NPL 1, thedeformation of a package substrate is prevented from transmitting to theangular velocity sensor chip.

CITATION LIST Patent Literature

PTL 1: JP-A-2010-243479

PTL 2: JP-A-2002-296293

PTL 3: JP-A-2007-64753

PTL 4: JP-A-2010-181392

Non Patent Literature

NPL 1: TRANSDUCERS 2013, pp. 1962-1965

SUMMARY OF INVENTION Technical Problem

In PTL 3, the leads are placed on two facing sides of the sides of thepackage substrate on which the detecting element is mounted, andtherefore, the influence of an unwanted signal from a direction in whichthe leads are placed can be suppressed. However, the sensor of PTL 3 issusceptible to the influence of an unwanted signal caused by twist ortilt toward a direction in which the leads are not disposed.

In the dynamic quantity sensor disclosed in PTL 4, since theanti-vibration member is provided between the sensor element and thecasing, there is a risk that the deformation of the anti-vibrationmember affects a detection signal of the dynamic quantity sensor.

In NPL 1, although the sensor chip is suspended by a bonding wire, thereis a risk that the wire may be broken due to vibration or the likeapplied to the sensor, and there is room for improvement in terms ofdurability or reliability.

The invention has been made focusing on the problem described above, andit is an object of the invention to provide a physical quantity sensorin which the influence of deformation of a package substrate on themeasuring accuracy of a sensor element can be suppressed.

Solution to Problem

To solve the above problem, a physical quantity sensor according to theinvention is a physical quantity sensor that measures a physicalquantity, including: a sensor element that detects a predeterminedphysical quantity and outputs an electrical signal; a plurality of leadportions that are connected to the sensor element; and a packagesubstrate that accommodates the sensor element and the plurality of leadportions, wherein the plurality of lead portions are connected atproximal end sides thereof to the package substrate side, and connectedat distal end sides thereof to the sensor element side, and theplurality of lead portions support the sensor element in such a mannerthat the sensor element does not contact the package substrate and thatthe transmission of deformation of the package substrate side to thesensor element is suppressed.

Advantageous Effects of Invention

According to the invention, since the plurality of lead portions supportthe sensor element in such a manner that the sensor element does notcontact the package substrate and that the transmission of deformationof the package substrate side to the sensor element is suppressed, theinfluence of deformation of the package substrate on a detection signalof the sensor element is reduced, and thus the measuring accuracy of thesensor element can be increased.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an exploded perspective view of a physical quantity sensoraccording to a first example.

FIGS. 2A and 2B are cross-sectional views of the physical quantitysensor.

FIG. 3 is an exploded perspective view of a physical quantity sensoraccording to a second example.

FIGS. 4A and 4B are cross-sectional views of the physical quantitysensor.

FIG. 5 is an exploded perspective view of a physical quantity sensoraccording to a third example.

FIGS. 6A and 6B are cross-sectional views of the physical quantitysensor.

FIG. 7 is a plan view of a lead substrate of a physical quantity sensoraccording to a fourth example.

FIG. 8 is a cross-sectional view of a physical quantity sensor accordingto a fifth example.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the invention will be described based onthe drawings. In the embodiment, as will be described in detail below,the influence of a physical quantity (temperature, humidity, unwantedvibration) other than a measurement target on a physical quantity sensorchip 10 is suppressed. To this end, in the embodiment, the physicalquantity sensor chip 10 as a “sensor element” is placed on a leadsubstrate 20 having a rectangular shape. Hereinafter, the physicalquantity sensor chip 10 is sometimes abbreviated as the sensor chip 10.

Leads 22 as “lead portions” are disposed at predetermined intervals oneach of four sides of the lead substrate 20. The lead substrate 20 issuspended in a package substrate 30 by means of the leads 33 extendingfrom the four sides. The surface of the sensor chip 10 and the rearsurface of the lead substrate 20 are slightly separated respectivelyfrom the inner surfaces of the package substrate 30, so thatpredetermined gaps are formed.

The sensor chip 10 and the lead substrate 20 are supported in asuspended state in the hollow package substrate 30, and are not incontact with the package substrate 30. For this reason, the influence ofan impact or deformation applied to the package substrate 30 on thesensor chip 10 can be suppressed.

Further, the gap formed between the surface of the sensor chip 10 andthe inner surface of the package substrate 30 and the gap formed betweenthe rear surface of the lead substrate 20 and the inner surface of thepackage substrate 30 are used as so-called gas dampers, so thatvibration transmitting from the package substrate 30 to the sensor chip10 or the lead substrate 20 can be attenuated.

Further, the plurality of leads 22 are disposed at predeterminedintervals on the four sides of the lead substrate 20 formed into arectangular shape, which is a symmetrical shape, and thereforesymmetrically support the lead substrate 20 and the sensor chip 10 fromfour directions. For this reason, in the embodiment, the transmission oftwist or tilt caused in the package substrate 30 to the sensor chip 10can be suppressed. In other words, in the embodiment, since vibration,twist, or tilt caused in the package substrate 30 can be absorbed by theplurality of leads 22, the influence of a physical quantity other than ameasurement target is reduced, and S/N can be increased.

Further, a difference between the linear expansion coefficient of thesensor chip 10 and the linear expansion coefficient of the leadsubstrate 20 is set to be small, or a predetermined board 50 having alinear expansion coefficient similar to that of the sensor chip 10 maybe provided on a surface of both surfaces of the lead substrate 20,which is on the side opposite to the surface on which the sensor chip 10is mounted. The predetermined board 50 is, for example, an amplifiercircuit board that amplifies a detection signal of the sensor chip 10.Due to this, the deformation of the lead substrate 20 due to thermalexpansion can be suppressed. When the linear expansion coefficients ofthe sensor chip 10 and the lead substrate 20 are approximately equal toeach other, the deformation of the lead substrate 20 can be suppressedeven when temperature changes. When the linear expansion coefficients ofthe sensor chip 10 and the lead substrate 20 are different from eachother, the predetermined board having a linear expansion coefficientsimilar to that of the sensor chip 10 is provided on the surface of bothsurfaces of the lead substrate 20, which is opposite to the mountingsurface of the sensor chip 10. Due to this, even when a temperaturechange occurs, the thermal expansion of the sensor chip 10 caused on onesurface of the lead substrate 20 and the thermal expansion of thepredetermined board 50 caused on the other surface of the lead substrate20 can be eventually cancelled out, and thus the deformation of the leadsubstrate 20 and the sensor chip 10 can be suppressed.

Further in the embodiment, since the leads 22 are formed as a lead framehaving a rigidity higher than that of a bonding wire, the lead substrate20 on which the sensor chip 10 is placed can be supported uniformly andfirmly. Hereinafter, the embodiment will be described in detail.

EXAMPLE 1

A first example will be described using FIGS. 1 and 2. FIG. 1 is anexploded perspective view of a physical quantity sensor 1 according tothe example. FIG. 2 are cross-sectional views of the physical quantitysensor.

The physical quantity sensor 1 is, for example, a device that detects apredetermined physical quantity (physical quantity as a measurementtarget) such as acceleration or angular velocity, and outputs a signal.The physical quantity sensor 1 is configured to include, for example,the sensor chip 10, the lead substrate 20, and the package substrate 30.

When a physical quantity as a measurement target is applied, athree-dimensional structure in the interior of the sensor chip 10 isdeformed, and the sensor chip 10 outputs an electrical signal. Thesensor chip 10 uses a change in capacitance or a change in resistance inresponse to the deformation of the three-dimensional structure toconvert the deformation into an electrical signal. The sensor chip 10 isformed into a symmetrical shape. Examples of the symmetrical shapeinclude, in a plan view, an oblong, a square, an isosceles triangle, aregular triangle, a circle, and an ellipse. A square or a circle is oneof preferable shapes for the sensor chip 10. However, the sensor chip 10is not limited to a square or a circle.

The lead substrate 20 is a substrate for electrically connecting thesensor chip 10 with the package substrate 30 to connect the sensor chip10 to an external system outside the figure. The lead substrate 20includes, for example, an electrode substrate 21, the leads 22, andconnecting elements 23.

The electrode substrate 21 is formed into a symmetrical shape from amaterial having a linear expansion coefficient similar to that of thesensor chip 10. Examples of the symmetrical shape include, in the planview, for example an oblong, a square, an isosceles triangle, a regulartriangle, a circle, and an ellipse. A square or a circle is one ofpreferable shapes for the electrode substrate 21 of the lead substrate20. However, the shape of the electrode substrate 21 is not limited to asquare or a circle.

In the example, the sensor chip 10 and the electrode substrate 21 of thelead substrate 20 are both formed into the same symmetrical shape (asquare herein). Then, equal numbers of the plurality of leads 22 aredisposed at predetermined intervals on respective four sidesconstituting the peripheral edge of the electrode substrate 21. Theleads 22 are formed as a lead frame having a rigidity higher than thatof a bonding wire.

A proximal end side of each of the leads 22 is electrically connected toan electrode 33 of the package substrate 30 with solder or the like. Adistal end side of each of the leads 22 is electrically connected via awiring pattern (not shown) of the electrode substrate 21 to the sensorchip 10 with solder or the like. Note that the leads 22 are fixed to theelectrode substrate 21 with solder or the like and thereby mechanicallyconnected to the sensor chip 10. The leads 22 uniformly support thesensor chip 10 in a suspended manner in the package substrate 30, viathe electrode substrate 21 of the lead substrate 20, from the four sidesof the electrode substrate 21.

The connecting elements 23 for electrically connecting with an electriccircuit in the sensor chip 10 are disposed at predetermined positions onthe surface (upper surface in FIG. 1) of the electrode substrate 21.

The package substrate 30 has a hollow sealed structure to accommodatethe sensor chip 10 and the lead substrate 20. The package substrate 30is formed into a square (in the plan view) as a symmetrical shape,similarly to the sensor chip 10 and the lead substrate 20.

The package substrate 30 includes, for example, a lid portion 31 and asubstrate portion 32. The electrodes 33 are disposed on the surface ofthe substrate portion 32 of the package substrate 30. The electrodes 33are electrically connected to the external system outside the figure viaother electrodes 34 shown in FIG. 2. The sensor chip 10 is electricallyconnected to the external system via the lead substrate 20 and thepackage substrate 30.

An example of the manufacturing process of the physical quantity sensor1 will be briefly described. Firstly, the sensor chip 10, the leadsubstrate 20, and the package substrate 30 are manufactured andprepared. Secondly, the sensor chip 10 is mounted on the lead substrate20, and the sensor chip 10 and the lead substrate 20 are electricallyand mechanically connected. Thirdly, the lead substrate 20 on which thesensor chip 10 is mounted is electrically and mechanically connected tothe substrate portion 32 of the package substrate 30. Fourthly, the lidportion 31 is hermetically attached to the substrate portion 32 so as tocover the substrate portion 32. The package substrate 30 is hermeticallysealed in a state where an inert gas or dry air is enclosed in theinterior thereof.

Reference is made to FIG. 2. FIG. 2(a) is a cross-sectional view of thephysical quantity sensor 1 after assembling. FIG. 2(b) is across-sectional view showing, in an enlarged manner, a portion of FIG.2(a).

The lead substrate 20 on which the sensor chip 10 is mounted issupported in a suspended state in the package substrate 30 by the leads22 extending from the four sides. Other portions except the proximal endsides of the leads 22 connected to the substrate portion 32 of thepackage substrate 30, that is, the sensor chip 10 and the electrodesubstrate 21, are supported by the leads 22 in such a state as to floatin the air without contacting the package substrate 30.

A minute gap δ1 is formed between the surface (upper surface in FIG. 2)of the sensor chip 10 and the rear surface of the lid portion 31 of thepackage substrate 30. Another minute gap δ2 is formed between the lowersurface of the electrode substrate 21 of the lead substrate 20 and theupper surface of the substrate portion 32 of the package substrate 30.These gaps δ1 and δ2 are set to, for example, values of from several μmto ten and several μm.

According to the example configured as described above, even when thepackage substrate 30 is deformed due to a change in temperature orhumidity, the leads 22 absorb the deformation through a slightdeflection or the like. Therefore, the influence of deformation of thepackage substrate 30 on the sensor chip 10 can be suppressed. As aresult of this, the physical quantity sensor of the example can improvemeasuring accuracy and reliability even when the physical quantitysensor is downsized or thinned.

According to the example, the lead substrate 20 on which the sensor chip10 is mounted is supported in a suspended state in such a manner thatthe lead substrate 20 except the proximal end sides of the leads 22 isnot contact with the package substrate 30, in the package substrate 30with a hollow structure. Then, the gap δ1 is formed between the sensorchip 10 and the lid portion 31 of the package substrate 30, and the gapδ2 is formed between the lead substrate 20 and the substrate portion 32of the package substrate 30. That is, in the example, the minute gaps δ1and δ2 are formed respectively above and below a structure of the sensorchip 10 and the lead substrate 20, and the gaps δ1 and δ2 function asgas dampers. Therefore, in the example, when unwanted vibration isapplied to the physical quantity sensor 1, the unwanted vibration can bereduced by damping effects of gases caused in the gaps δ1 and δ2. Forthis reason, the intensity of a signal for the sensor chip 10 to detectthe unwanted vibration is made smaller than the intensity of a signal ofa physical quantity as a measurement target, so that S/N can beincreased.

In the example, even when a resonant frequency is applied to athree-dimensional structure in which the sensor chip 10 and the leadsubstrate 20 are weights and the leads 22 are springs, the transmissionof vibration due to the resonant frequency to the sensor chip 10 can besuppressed by the gas damper effects of the gaps δ1 and δ2.

In the example, since the leads 22 extracted from the electrodesubstrate 21 of the lead substrate 20 are disposed in the directions ofthe four sides of the electrode substrate 21, the deformation of thelead substrate 20 when unwanted vibration is applied to the packagesubstrate 30 can also be suppressed. Since the lead substrate 20 onwhich the sensor chip 10 is mounted is uniformly supported at the foursides by the leads 22 having a high rigidity, the rotation of the sensorchip 10 and the lead substrate 20 about the Z-axis in FIG. 1, therotation thereof about the X-axis, or the rotation thereof about theY-axis can be suppressed. Then, as described above, when the whole ofthe sensor chip 10 and the lead substrate 20 is displaced in thevertical direction (Z-axis direction), the gaps δ1 and δ2 block themovement in the vertical direction, and therefore, the displacementamount in the vertical direction can be reduced.

EXAMPLE 2

A second example will be described with reference to FIGS. 3 and 4. Thefollowing examples including the example correspond to modified examplesof the first example, and therefore, the differences from the firstexample will be mainly described. A physical quantity sensor 1A of theexample incorporates the amplifier circuit board 50 therein. FIG. 3 isan exploded perspective view of the physical quantity sensor 1A. FIG. 4are cross-sectional views of the physical quantity sensor 1A.

The physical quantity sensor 1A is configured to include the sensor chip10, the lead substrate 20, a package substrate 30, and the amplifiercircuit board 50. The amplifier circuit board 50, which is an example ofthe “predetermined board” that processes a signal from the sensor chip10, amplifies a signal of the sensor chip 10 and outputs the signal.Hereinafter, the amplifier circuit board 50 is sometimes abbreviated asthe circuit board 50.

The circuit board 50 is formed into a square or an oblong as asymmetrical shape. The circuit board 50 is accommodated in a circuitboard accommodating portion 35 formed at the center of a substrateportion 32A of the package substrate 30A, and is electrically connectedwith electrodes 36 provided on the substrate portion 32A. The sensorchip 10 is connected from, for example, the leads 22 via the electrodes33 of the package substrate 30 to a wiring pattern (not shown) in thesubstrate portion 32, and is connected from the wiring pattern via theelectrodes 36 to the circuit board 50.

An example of the manufacturing process of the physical quantity sensor1A will be described. Firstly, the sensor chip 10, the lead substrate20, and the package substrate 30 are manufactured and prepared.Secondly, the sensor chip 10 is mounted on the lead substrate 20, andthe sensor chip 10 and the lead substrate 20 are electrically andmechanically connected. Thirdly, the circuit board 50 is mounted on theaccommodating portion 35 of the package substrate 30, and electricallyconnected with the electrodes 36. Fourthly, the lead substrate 20 onwhich the sensor chip 10 is mounted is electrically and mechanicallyconnected to the substrate portion 32 of the package substrate 30.Fifthly, the lid portion 31 is hermetically attached to the substrateportion 32 so as to cover the substrate portion 32. The packagesubstrate 30 is hermetically sealed in a state where an inert gas or dryair is enclosed in the interior thereof.

Also in the example, the minute gap δ1 is formed between the uppersurface of the sensor chip 10 and the lid portion 31 of the packagesubstrate 30. Further, the minute gap δ2 is also formed between thelower surface of the electrode substrate 21 of the lead substrate 20 andthe substrate portion 32 of the package substrate 30. More specifically,in the example, since the circuit board 50 is accommodated in theaccommodating portion 35 at the central portion of the substrate portion32, the gap δ2 is defined as a gap between the upper surface of thecircuit board 50 or the upper surface of the substrate portion 32,whichever is a higher surface, and the lower surface of the electrodesubstrate 21 of the lead substrate 20. That is, the sensor chip 10 andthe lead substrate 20 are also not in contact with the circuit board 50.

The example configured as described above also provides operationaleffects similar to those of the first example. Further, since thephysical quantity sensor 1A of the example incorporates the circuitboard 50 therein, a signal of the sensor chip 10 can be amplified andoutput to the external system, and thus convenience is improved. Thecircuit board 50 may include a circuit that exerts a function other thanthat of an amplifier circuit. For example, a waveform shaping circuit, anoise filtering circuit or the like may be included in the circuit board50, or an analog/digital conversion circuit or the like may be includedin the circuit board 50.

EXAMPLE 3

A third example will be described using FIGS. 5 and 6. A physicalquantity sensor 1B of the example includes a circuit board 50B mountedon the lower surface of the electrode substrate 21 of a lead substrate20. Further, in the physical quantity sensor 1B of the example, leads 22are slightly bent so as to forma space for disposing the circuit board50B between the lower surface of the electrode substrate 21 and theupper surface of the substrate portion 32. FIG. 5 is an explodedperspective view of the physical quantity sensor 1B. FIG. 6 arecross-sectional views of the physical quantity sensor 1B.

The physical quantity sensor 1B is configured to include the sensor chip10, the lead substrate 20B, the package substrate 30, and the circuitboard 50B. The leads 22B are bent obliquely downward and extracted, asshown in FIG. 6, from the four sides of the electrode substrate 21 ofthe lead substrate 20B.

When the electrode plate 21 is assumed as a reference horizontal plane,the lead 22B extends obliquely downward by an angle θ from thehorizontal plane. A distal end side of the lead 22B is a flat portionconnected to the electrode plate 21, and a proximal end side of the lead22B is a flat portion connected to the electrode 33 of the packagesubstrate 30.

The lead substrate 20B on which the sensor chip 10 is mounted issupported, by the leads 22B obliquely bent by the angle θ from thehorizontal direction, in a suspended state in the package substrate 30with a hollow structure. A gap δ2B between the electrode substrate 21 ofthe lead substrate 20 and the substrate portion 32 of the packagesubstrate 30 is larger than the gap δ2 in the examples described above(δ2B>δ2) by an amount corresponding to the inclination of the leads 22B.The circuit board 50B is mounted at the central portion of the lowersurface of the electrode plate 21 while being located in this expandedgap δ2B.

The circuit board 50B, which is another example of the “predeterminedboard”, is formed into a square or an oblong as asymmetrical shape. Thecircuit board 50B may be an amplifier circuit board that amplifies asignal from the sensor chip 10, or may be a circuit board that realizesa function other than amplification. On the circuit board 50B, aplurality of electrodes 51 for electrically connecting with the leadsubstrate 20B are formed.

The circuit board 50B is located at substantially the central portion ofthe electrode plate 21 of the lead substrate 20, and fixed to the lowersurface by soldering or the like. The circuit board 50B is formed so asto have a linear expansion coefficient approximately the same as that ofthe sensor chip 10. Due to this, even when a temperature change occursin the physical quantity sensor 1B, a displacement due to the thermalexpansion of the sensor chip 10 and a displacement due to the thermalexpansion of the circuit board 50B are cancelled out by each other asviewed from the lead substrate 20. Therefore, the displacement amount ofthe lead substrate 20 can be reduced, and an influence due to adifference between the linear expansion coefficients on the sensor chip10 can be suppressed. Note that if not only are the respective linearexpansion coefficients of the sensor chip 10 and the circuit board 50Bset approximately equal to each other, but also the linear expansioncoefficient of the electrode substrate 21 of the lead substrate 20 ismade approximately equal to the linear expansion coefficients, theinfluence due to thermal expansion can be still further reduced.

An example of the manufacturing process of the physical quantity sensor1B will be described. Firstly, the sensor chip 10, the lead substrate20B, and the package substrate 30 are manufactured and prepared.Secondly, the sensor chip 10 is mounted on the lead substrate 20B, andthe sensor chip 10 and the lead substrate 20B are electrically andmechanically connected. Thirdly, the circuit board 50B is mounted on thelead substrate 20B, and the circuit board 50B and the lead substrate 20Band the sensor chip 10 are electrically connected via the electrodes 51.Fourthly, the lead substrate 20B on which the sensor chip 10 and thecircuit board 50B are mounted is electrically and mechanically connectedto the substrate portion 32 of the package substrate 30. Fifthly, thelid portion 31 is hermetically attached to the substrate portion 32 soas to cover the substrate portion 32. The package substrate 30 ishermetically sealed in a state where an inert gas or dry air is enclosedin the interior thereof.

The example configured as described above also provides operationaleffects similar to those of the first and second examples. Further inthe example, since the circuit board 50B is mounted on the leadsubstrate 20B while being located on the side opposite to the sensorchip 10, a wiring pattern length between the circuit board 50B and thesensor chip 10 can be shortened. Therefore, the superimposition of noiseon the signal of the sensor chip 10 can be suppressed, so thatreliability and usability can be still further improved.

EXAMPLE 4

A fourth example will be described using FIG. 7. In a physical quantitysensor 1C of the example, the leads 22 as “first lead portions” anddummy leads 22C as “second lead portions” are extracted from theelectrode substrate 21 of a lead substrate 20C. In FIG. 7, the leads 22are hatched to distinguish them from the dummy leads 22C.

The leads 22 electrically connect the sensor chip 10 with the packagesubstrate 30 as described above, and also mechanically connect thesensor chip 10 to the package substrate 30 via the electrode substrate21.

In contrast to this, the dummy leads 22C only mechanically connect thesensor chip 10 to the package substrate 30 via the electrode substrate21, so that the dummy leads 22C are not electrically connected to thesensor chip 10. That is, the dummy leads 22C function only as beams forsupport, and do not constitute an electric circuit.

Since an electrical signal flows through the normal lead 22, a distalend of the lead 22 is provided on the electrode plate 21 while beinglocated in a predetermined region to which a stress due to a temperaturechange is hardly applied. The predetermined region is, for example, thecentral portion of each of the four sides of the electrode substrate 21.Since the displacement amount due to thermal expansion is less at thecentral portion of the electrode plate 21, a stress applied to the lead22 can be made small. As a result of this, the superimposition of noiseon the signal flowing through the lead 22 can be suppressed.

The example configured as described above also provides operationaleffects similar to those of the first example. The example can also becombined with any of the second and third examples. According to theexample, the normal leads 22 are disposed in the region to which thestress is relatively hardly applied, while the dummy leads 22C throughwhich a signal does not flow are disposed in a region to which thestress is relatively applied; and therefore, reliability can be stillfurther improved.

EXAMPLE 5

A fifth example will be described using FIG. 8. FIG. 8 is across-sectional view of a physical quantity sensor 1D. In the physicalquantity sensor 1D of the example, the lead substrate 20 is removed, anda sensor chip 10D and a package substrate 30D are directly connected viaa plurality of leads 37.

A plurality of electrodes 11 are provided on the lower surface of thesensor chip 10D. The leads 37 corresponding to the electrodes 11 arebent obliquely upward and extracted from the substrate portion 32 of thepackage substrate 30D. A signal detected by the sensor chip 10D is sentto the external system via the electrodes 11, the leads 37, theelectrodes 33, and the electrodes 34.

The gap δ1 is formed between the upper surface of the sensor chip 10Dand the lid portion 31 of the package substrate 30D. Also, a gap δ1D isformed between the lower surface of the sensor chip 10D and thesubstrate portion 32 of the package substrate 30D.

The example configured as described above also provides operationaleffects similar to those of the first example. The example can becombined with any of the second, third, and fourth examples. In theexample, since the lead substrate 20 is removed, the configuration ofthe physical quantity sensor 1D can be simplified, and thus themanufacturing cost can be reduced.

Note that the invention is not limited to the embodiment describedabove. Those skilled in the art can make various additions,modifications or the like within the scope of the invention. Thefeatures described in each of the examples can be used in appropriatecombination with the configurations of the other examples. For example,the sensor chip and the lead substrate may be integrally formed.

REFERENCE SIGN LIST

-   1, 1A, 1B, 1C, 1D: physical quantity sensor-   10, 10D: sensor chip-   20, 20B, 20C: lead substrate-   22, 22B, 22C: lead-   30, 30A, 30D: package substrate-   37: lead-   50, 50B: circuit board

1. A physical quantity sensor that measures a physical quantity,comprising: a sensor element, that detects a predetermined physicalquantity and outputs an electrical signal; a plurality of lead portionsthat are connected to the sensor element; and a package substrate thataccommodates the sensor element and the plurality of lead portions,wherein the plurality of lead portions are connected at proximal endsides thereof to the package substrate side, and connected at distal endsides thereof to the sensor element side, and the plurality of leadportions support the sensor element in such a manner that the sensorelement does not contact the package substrate and that the transmissionof deformation of the package substrate side to the sensor element issuppressed.
 2. The physical quantity sensor according to claim 1,wherein the package substrate has a hermetic structure, and a gas damperis formed in a gap between the sensor element and the package substratedue to a gas enclosed in the package substrate.
 3. The physical quantitysensor according to claim 2, wherein the plurality of lead portionssymmetrically support the sensor element.
 4. The physical quantitysensor according to claim 3, wherein the sensor element, has asymmetrical shape, the plurality of lead portions are disposed atpredetermined intervals on a peripheral edge side of the sensor element,and the plurality of lead portions uniformly support the sensor element.5. The physical quantity sensor according to claim 4, wherein theplurality of lead portions are provided on a lead substrate, the sensorelement is mounted on the lead substrate, and the plurality of leadportions support the sensor element via the lead substrate.
 6. Thephysical quantity sensor according to claim 5, wherein a differencebetween a linear expansion coefficient of the lead substrate and alinear expansion coefficient of the sensor element is set to be small,or a predetermined board having a linear expansion coefficient similarto that of the sensor element is provided on one surface of bothsurfaces of the lead substrate, which is on the side opposite to theother surface on which the sensor element is mounted.
 7. The physicalquantity sensor according to claim 6, wherein the predetermined board isa board that processes an output signal from the sensor element.
 8. Thephysical quantity sensor according to claim 7, wherein the plurality oflead portions are formed as a lead frame having a rigidity higher thanthat of a bonding wire.
 9. The physical quantity sensor according toclaim 8, wherein the plurality of lead portions include a plurality offirst lead portions electrically and mechanically connected to thesensor element and a plurality of second lead portions mechanicallyconnected to the sensor element.
 10. The physical quantity sensoraccording to claim 9, wherein a distal end side of each of the firstlead portions is provided in a predetermined region where a stress whena force is applied to the lead substrate is small in the lead substrate.11. The physical quantity sensor according to claim 5, wherein the leadsubstrate is formed into a rectangular shape in a plan view, and theplurality of lead portions are disposed at predetermined intervals onfour sides of the lead substrate.